The Burden of a Promise
by Assassin040147
Summary: Making a promise that you intend to keep no matter what, can be a very heavy burden. A human that fell into a mountain has just learned that lesson. Will he keep his word, or will the burden break his integrity?
1. Chapter Prologue

**Disclaimer: I do not own Undertale. The game is the property of Toby Fox. If my OC is similar to any trademarked character and/or OC from another fanfic, it is purely coincidence.**

 **A/N: This is my very first fanfic I am making, so please excuse my grammatical mistakes. I do hope you enjoy the experience.**

' _Thinking'_

"Speech"

" **Empowered Speech"** (Used when casting magic)

 **Preview**

In a room was a man that had seemingly gone insane. Why you ask, well he was currently occupying himself with repeatedly punching a big door while crying out "Not again!" and "Why me!"

You see, he has a curse that was once thought to be a blessing. The ability to 'RESET' the timeline and load specific parts of the timeline, which he referred to as 'SAVE's. Using this ability, he quickly made friends with all the monsters, and would keep a promise that he wishes that he never made. Problem is he does not have the SAVE file to go back and prevent himself from ever making that promise.

After calming down from his little outbreak, the man slumped down to the ground. His eyes where empty as he bitterly reminisced about what brought him to this point, about that damn promise he made to a friend.

 _Flashback_

Standing in front of the door which would lead to freedom, was a man about average height. He was wearing a black leather biker jacket with soft blue shirt underneath, black pants with a leather belt, which had a silver buckle, and black steel toe boots. He had black hair, brown eyes, and an oval face with a short, neatly trimmed beard. The odd thing about his beard though, is that it has two red streaks that line his jaw, nearly coming together under his chin.

Standing not too far from him was a short skeleton, who wore an everlasting grin. He was in his trademark clothing, a blue hoodie, white shirt, black shorts and blue slippers. His name, Sans.

"Well kid, are you gonna break that barrier?" Sans asked.

"Yeah yeah, I'm just thinking."

"About?"

"Well, you remember that I told you about how dangerous it would be if another war broke out between monsters and humans?"

"Yes, you specifically told me about the military and their weapons, the fact that they outnumber us, and that they could even hunt us no matter where we are. Listen kiddo, I know that you worry about us, we are your friends and that you think that the other humans will reject us, but have a little faith would ya."

"Sorry Sans, it's not what I meant. What I meant was what if they experiment on you, or use you as sub-human labor or worse. If that happened I would never forgive my…" He was cut off by Sans letting out a small chuckle.

"You seem to take well after your MOMster, you worry way too much."

The man just stares at Sans with a flat look. Shaking his head he approaches the barrier, which can only be broken at the door for some reason, and places his hand on it. He starts to concentrate as hard as he can, and he feels something pull at the back of his mind. Next thing he knows he is a white room with a person standing in front of him. This new person waved a staff and a pulse was sent out. The pulse returned and the person nodded. Casting his gaze at the one that summoned him, he simply said "The barrier will not break, not until every monster that is in this cave has been killed." With that said he disappeared and the room went black.

"KID! KID! ARE YOU OK! COME ON, DO SOMETHING AT LEAST!" The man wakes up to Sans that was shaking him and screaming at him.

"Sans? How long was I out?"

"About five minutes. What happened? Why is the barrier still up? And what was that pulse?"

The last question really caught the man by surprise, if what that vision said was true, would he have to kill all his friends and family to break the barrier?

"Sans"

"Yes?"

"I got a vision, and it was a bad one. I know how to break the barrier, but to do so… it will not be worth it and will take a lot of time."

He looked and Sans and immediately regretted saying that. Sans was furious.

"Not worth it? NOT WORTH IT?! Is it not worth freeing the monsters? Is it not worth our hopes and dreams? HOW COULD YOU SAY THAT?!"

"Sans Listen to…"

"NO YOU LISTEN! What are you thinking? Promise me! If there is a way to break the barrier then you will."

"S-Sa-ans"

"Please, Tristan I beg you."

"Sans I, I don't know what to say." The newly identified Tristan said.

"Just say yes."

"Are you sure?"

"Yes"

"Fine I will."

 _Flashback End_

Tristan just sat there, wallowing in sadness. ' _How long ago was that? 812 or 813 RESETs ago? I can barely remember it now'_. He had done a lot of research, because if he was gonna break the barrier. Then he would find a way to bring his friends back. He found out that with a special bit of magic, he could save their souls inside of him. He even found out how to recreate their bodies and put their souls back into the bodies. But, and there is always a but, he has to kill _All_ the monsters, and that is where a wildcard appears. You see, a specific monster that goes by the name of WD Gaster that only appears on rare occasions, when certain conditions occur, and only after all the monsters are dead.

The conditions are as follows: 1, In a previous 'run through' as he calls it, he must be a pacifist. 2, He must kill everyone (1). And 3, He must enter Gaster's Laboratory, which Dr. Alphys did a great job of making it very difficult to enter.

' _It hurts so much to have to do this. I made that promise, I will keep it, but seeing their faces so happy, and then killing them in the next run. I don't know anymore, how many times I had to do that. O yeah, 406 to 407 times. The genocides though, seeing the hate in Sans' eyes. How I have to decline his begging to reset and bring his brother and friends back. Toriel's look of pain, and betrayal when she realizes that I am going to kill her. Papyrus saying that he still believes in me. Undyne that wants revenge for killing her friends. Alphys, her reaction, her words. Mettaton believing she can still be fixed. Napstablook, Asgore, all of them.'_

He had just completed his pacifist run and broke down in the one place he knows is private. Well after he alludes Sans that is. _'Speak of the devil'_ he though as Sans walked in. Curious the skeleton wandered over to his friend when he saw the condition Tristan was in.

"What's wrong kid? Looks like someone killed your puppy or something?"

"Sans, do you think I'm a good person?"

"Where is that coming from? Well yeah I do think so. Are you ok?"

"Yes just thinking" _'though you probably don't know what I'm talking about'_ he added in his mind.

"Are you sure? Cat got your tongue? 'Cause I think now is a PURRfect time to talk with someone."

"You and your puns, listen I can't break the barrier. Something is blocking me from doing so." He smoothly lied. It was easier to lie now seeing as he would RESET soon anyways.

"Are you sure?"

"Well you did ask why I was feeling down."

"True, but if you though being a better person would change the way the barrier works, then you would have to become a saint." Sans gave him a piece of paper.

Tristan looked at the paper and chuckled. The paper was cut to ribbons at the end with the words 'TAKE ONE FOR A TEARABLE PUN' written on it.

"Who else would laugh at my puns, well except Toriel?"

"Touché."

"Well I'm heading to Grillby's, want to come with? I know a shortcut."

"Thanks but no thanks Sans, I'm a bit tired, so I'll head home for now."

After saying their goodbyes, the two split up. One heading to Grillby's, the other about to press RESET, and start his personal hell once again.

END

 **A/N: Don't worry Frisk and Chara both exist. All will be explained in future chapters.**

 **I hope you enjoyed the read. As said before this is my first fanfic, so please go easy on me with the criticism. If you have any ideas you would like to share PM me and I will see about adding them to the story. Also if you have any Sans puns could you PM me some, I am not very creative with puns.**


	2. Chapter 1

**Disclaimer: I do not own Undertale. The game is the property of Toby Fox. If my OC is similar to any trademarked character and/or OC from another fanfic, it is purely coincidence.**

' _Thinking'_

"Speech"

" **Empowered Speech"** (Used when casting magic)

 **Chapter 1: How could I Forget**

Waking up, lying face down on a bed of golden flowers, Tristan awoke to a feeling that he is all too familiar with, the feeling of remorse. He knew that he would have to do the unthinkable. He would soon have to start the genocide run.

Letting out a groan, he swiftly stood up. Regaining his bearings, he started to walk down the only visible corridor, noting that the walls where an eerie dark color. Soon he entered the chamber where he would have his first kill.

The chamber had the same color scheme that was present all the way in his short trek. Grey flooring with dark, eerie walls. At the center of the chamber was a small patch of grass, where his soon to be pray would sprout from, that was underneath a light source. Where the light came from he would never know, but one thing was clear. He would have to steel his heart for the confrontation, as Flowey would definitely hide from him if he missed his chance.

Taking a calming breath and donning his best 'mask' of a newcomer, he approached the grass patch. Flowey sprouted from the soil and introduced himself.

"Howdy. I'm Flowey. Flowey the flower. Hmm… you seem to be new to the Underground, aren't tcha?" Tristan just nodded, giving his best look of wonder at seeing a talking flower.

"Golly, you must be confused. Someone ought to teach you how things work around here. I guess little old me will have to do. Ready? Here we go."

Suddenly the room turned black and his soul appeared, taking the shape of a floating heart, hovering right in front of his chest. The odd thing though was that the heart was black, which he knew symbolized his grief. Flowey also took noticed, and started to ponder what the color meant. Knowing he would not get another easy opening, Tristan lunged for Flowey and managed to get a secure grip on his stem. Before Flowey could even react, he was ripped out of the ground and a glowing hand placed on his head. Tristan gave a heavy sigh as Flowey slumped in his hand, knowing that he had just killed the monster all the while saving and storing the soul in a special place. A place where the 'pulse' cannot find it.

Tristan quickly disposed of the body. Lighting it on fire with a fireball, which he summoned from his hand. For some reason, only Flowey's body would not turn to ash after death. All the other monsters did, something that still ponders him till this day.

As he finished, he heard footsteps. Toriel was about to enter the chamber, so he quickly used a wind spell to get rid of the dust and smell. You see, it seemed the longer he stayed in the Underground, the more magical abilities he gained. He had done some research and discovered that at a time, all humans were capable of magic, and had an inactive reservoir hidden within them. He assumed that with all the magic in the air, it started to awaken his dormant abilities, granting him the ability to manipulate wind, fire and water.

He began walking to the door, acting very confused. When Toriel entered the chamber and saw him, she immediately rushed towards him. As she moved, he took in her form. She seems to be a bipedal goat monster with white fur, long eye lashes and two visible fangs. She wore a purple robe with white sleeves and the Delta ruin on her chest.

"A human? That has fallen? Are you alright? Are you injured?"

"No I'm fine. If I may ask, where am I? And what are you? Who are you?"

Toriel seemed a bit dumbfounded, and then realized that she has yet to introduce herself.

"Sorry, I was just a bit worried. My name is Toriel, and you are currently in the ruins of the Underground. As for what I am, well I am a monster, but don't be frightened. I will not harm you." She said in a calming manner.

"Ookaay, well my name is Tristan. I guess it is a pleasure to meet you, umm Toriel."

"It is a pleasure meeting you as well. I should get you somewhere safe, please give me your hand." She replied as she stretched out her hand, beckoning him to take a hold of it. Soon the two were crossing chambers and completing the puzzles. He does not know when, but the color scheme changed some time ago. The walls and flooring where a shade of purple, with a lighter shade indicating pathway. Tristan had enjoyed the moment, silently lamenting the fact that soon, he would have to kill his adoptive mother who was leading him through the chambers. He had made sure to save at the 'checkpoints' as he passed them. Making a mental note to come back to kill any monsters that he missed due to Toriel's presence. Soon they arrived in a chamber with what appeared to be a training dummy.

Toriel turned to Tristan and asked "You see that dummy over there? When you come across a monster while I am not present, just strike up a friendly conversation until I come. You could also try to resolve the problem on your own. Could you give it a try with the dummy, for me?"

He walked over to the dummy, and told it that he would like to be friends. Naturally the dummy did not reply, but he did discreetly place a glowing hand on its head, sucking out the soul that was inhabiting the dummy.

As he walked back to Toriel, he noted that she looked quite happy. He chuckled as she congratulated him. Soon the two were walking through a very long hall. He knew what Toriel was about to say as she turned to him.

"Can I ask you a favor? I want you to walk down to the end of the hall. Do not fear for I will be waiting for you at the end."

She did not even give him a chance to respond before she quickly walked off. He let out a sigh as he started to walk to the end of the hall. After about five minutes of walking, he came up to a column made of a white material. He knew Toriel was standing behind it, but he pretended not to notice. As he passed the column, Toriel stepped out from behind the column.

"Don't be scared, I am right here. I am sorry my child, but I had to know if you were able to be independent."

"It is fine Toriel, but I am a twenty year old, so I think I am a bit too mature to be called a child."

"O I have not thought to ask your age. Though compared to a monster you are still quite young, so please bear with me."

"Ok Toriel, I won't mind."

"Thank you for understanding, let's keep moving. I want you to be safe."

As the two were traversing a room, a Froggit appeared and hopped towards Tristan. A Froggit was a type of frog monster with white skin and black eyes. It was also much larger than a normal frog, being about the same size as the average human child. If he would fight, Toriel would not be happy. Instead he opted to compliment the Froggit. It seemed that it did not understand, though it apparently felt flattered and gave him a smile. Now one would expect the Froggit to let them pass unhindered, it attempted to attack Tristan. Before it could though, Toriel gave it quite the glare and it backed down and hopped away.

"I am so proud that you actually took my lesson to heart." Toriel said.

Tristan just rubbed the back of his head and let out a nervous chuckle. Toriel did not seem to notice as she kept on walking. Eventually she stopped and asked him whether he liked cinnamon or butterscotch, but seemed to remember that he preferred butterscotch. He sniggered at the confused look that Toriel's face had adopted. Even though he found a way to prevent sans from remembering past a certain amount of RESETs, he never knew how Toriel could remember, even after he had done the same thing to her like he did Sans. 'Must be paternal instincts combined with a mother's love.' He thought.

"Regardless, you are not against cinnamon are you? For example, if I were to give it to you on a plate, would you turn up your nose?" she continued.

Remembering that she once actually gave him a plate of cinnamon for breakfast, Tristan quickly replied "I don't have anything against cinnamon, but I can't just eat it without anything. You see, cinnamon is a very dry powder that is normally used as an ingredient or a spice. If I where to eat it just like that, it would cause quite a mess as I would only end up coughing it all out as it dries and irritates my throat."

"Ah I see."

Wiping the sweat off of his forehead, Tristan congratulated himself for avoiding that problem. Not long thereafter, Toriel stopped him and told him that she wishes for him to stay where he was. She would be back soon apparently. When she had left and was gone for a good three minutes, his eyes seemed to change to a steely cold glare. He turned around and started going back in the direction he just came from, as he had some monsters that he had to ignore due to a certain motherly figure that just left him alone. Soon he found that Froggit that had approached him earlier. Silently he came from behind and placed a glowing hand on the monster's head. Slumping down, the Froggit's body quickly turned to ash. Tristan felt a warm liquid running down his cheeks. He did not need to check what it was, he already knew that he was tearing up. After all, who would not after remembering that this is the same Froggit that was his first kill, before he knew how to save their soul.

 _Flashback_

He was finally alone, Toriel had just left. Now don't get him wrong, he did love his adoptive mother, but right now he needed to be alone. He started to walk in the opposite direction that Toriel had just gone. He had a couple of monsters that he had to take care of.

Soon he saw the Froggit that had approached him earlier. When the Froggit noticed him, the world had gone black, indicating the beginning of the battle. Deciding to attack first, Tristan lunged and managed a successful punch to Froggit's face. The force was enough to launch the Froggit about a meter. Getting back up, the monster was not too happy. Suddenly the monster lunged at the human's soul. Just barely managing a dodge, Tristan's foot shot out and connected on the Froggit's soft stomach. As the monster flew up into the air, it started to turn to ash. Regaining his footing, Tristan launched himself into the air, hoping to grab the, now exposed, soul. As he landed, he saw that he had captured the souls, but all for naught. The soul had just disintegrated within his hand.

Widening his eyes in shock, he just stared at the empty space where the soul had once inhabited. Confusion and denial soon had their ugly grasp on his heart.

' _What? Why? What's going on, why did his soul just… just do that? How, how can I save them if that will just happen again? Sans! Sans will know, or at least have an idea! He was a scientist once! Yes! He must know, he can't not know right?_ '

With that small bit of a morale booster, he started walking back in the direction of Toriel's home. Back to his home.

 _Flashback end_

That moment still haunts him till this day. Though he will still continue his genocide, he made a promise after all. Once he was done killing all the monsters that he had to ignore, and the ones that laid ahead, he notice that he at a fork in the road. If he went straight, he would go to a balcony overlooking a small city. He would have to make a visit after dealing with Toriel. If he turned left though he would go to Toriel's home, most likely finding her about to go searching for him.

Deciding that he was a bit tired, he went down the left hallway. As expected, he found a quaint little house with a dead tree in the front yard. Red flowers surrounded the tree and grew along some of the walls. All in all, it looked quite peaceful. He could not quite place it, but he felt that he was forgetting something. ' _If it is important, I would not have_ forgotten.' He reasoned. He then heard rapid footsteps from the house and let out a small chuckle. Hiding behind the tree, he waited for Toriel.

Soon he saw her about to run straight past him, she would have had he not jumped out from behind the tree. Bracing him-self as he knew she would not stop in time.

"Boo"

Needless to say there was a load thud as their two bodies collided. Rubbing his head, he gave a sheepish chuckle at the look Toriel was sending him. She was totally surprised that he was here, but quite amused by the situation. Standing up, she started to apologize, but was interrupted by Tristan.

"No need to apologize Toriel. I disobeyed you by wandering off in the first place."

"Well I am quite happy that you are here. This was not the first time that I have left someone in that hallway to give them a surprise, only to end up finding her here instead… O dear, it seems that I have let my surprise slip."

"Well technically not, remember that you did not yet tell me what the surprise is."

"Well I guess you are right, but I must really learn to not do that again. What if you could have been hurt? Or worse, I don't want to think of the latter option."

"Well, I am quite fine. A little bit banged up from our fall, but not bad at all."

"Here let me heal you."

"Thanks Toriel."

After healing his injuries, Toriel started walking towards her home. Still not shaking the feeling that he forgot something of significant importance, Tristan followed not far behind. When they entered Toriel quickly told him to take a seat in the lounge area of her home. She also told him that she will be back soon. Taking a seat in one of the sofas, he looked around the room. He saw a bookshelf with a lot of books, a small reading lamp on a table, a dining table that could fit four people, and finally a photograph that was framed on the wall. The light was causing a glare on the glass, but staring at it made the feeling that he forgot something come back with a major force.

He stood up to look at the picture, but a feeling of foreboding washed over him. He approached the seemingly non-threatening object quite cautiously. Eventually he was right in front of the photograph. His eyes widened in horror at what he saw. There, standing in the middle was Toriel, with her hands on the shoulders of two girls. One had a light skin complexion, light brown hair and red eyes. She wore a green jacket with two yellow stripes running horizontally. The other had a darker skin complexion, brown hair, and her eyes where squinted. She wore a blue jacket with two purple stripes, also running horizontally. He remembers now. He remembers that he also had two adoptive little sisters, who he cherishes just as much, if not more than their adoptive mother. He was shaking with unshed tears in his eyes.

' _How? How could I forget about them? How could I forget about you two? Frisk, Chara I hope you two can forgive me._ '

He never noticed three sets of eyes watching him as he silently wept. Standing at the door, was Toriel and her two adopted human children.

 **End**

 **A/N: So yeah, I did not forget about those two. They will also have a vital role in the next chapter. Assassin040147 out.**


	3. Chapter 2

**Disclaimer: I do not own Undertale. The game is the property of Toby Fox. If my OC is similar to any trademarked character and/or OC from another fanfic, it is purely coincidence.**

' _Thinking'_

"Speech"

" **Empowered Speech"** (Used when casting magic)

 **Chapter 2: The Tragic Family Reunion**

They could not believe what they were seeing. This man that came out of nowhere was crying in front of their family portrait. Toriel did not know what to do, but she did know that Tristan was in pain. What caused said pain may have been unknown to her, but she felt that she should at least do something to hopefully cheer him up. Unknown to her, both Frisk and Chara were in a state of mixed feelings. On one hand, they felt that they knew him, therefore they were sad that he was feeling pain. On the other though, they were weary of him. They knew he was dangerous.

Not one of them knew what to do. It was a very strange circumstance that they found themselves in. Pushing aside her sense of danger, Frisk started to go towards Tristan. Half way there, frisk turned towards them and gave a determined look towards the rest of her family. Toriel and Chara saw this and decided that maybe they should also help in cheering him up. Unbeknownst to them, Tristan was reliving a particularly painful memory. The one where he had just killed his mother, only to find his two little sisters standing behind him with tears streaming down their faces.

 _Flashback_

Tristan was stunned at seeing them standing there. They were supposed to stay at the house while he and Toriel had gone to check the ruins for any fallen humans. The plan was simple but effective. He and Toriel had done so many times in the past, so why were they here now?

"Frisk, Chara, why are you here?" he asked in a somber tone. He felt absolutely horrible already, now he had possibly scarred them for life.

"Why?" Frisk had asked that in an utterly broken voice.

"Why did you do that to mom?"

"Frisk, I can explain."

"What is there to explain broth… NO! What is there to explain Tristan!?"

"Chara, please listen to…"

"NO! Why should we listen to you! You just killed our mother! Toriel had taken you in! She had given you a home, a family and you just… you just… killed her!"

With every word that Chara had said, he just felt worse and worse. After seeing Toriel's look of betrayal and her trying to reason with him, Chara's word felt like actual stabs. He could not afford to listen to Toriel's words, the temptation to just break his promise would rise to be too much to handle. So he had just blocked off the world, putting him in a place where it was only him and his objective. He could not afford to regret it now, he had a job to do. He shut off his world once again and steeled his heart. Looking his sisters in the eyes he took a step forward.

"Frisk, Chara. I am really sorry, but this must be done. I only hope that you will understand."

Seeing the look in their ex-brother's eyes, fear had gripped their hearts. They wanted to run, to scream, anything, but their bodies would not move. All they could do was to stare wide eyed as their soon to be killer approached.

"I really am sorry you two, but this must be done."

He placed a glowing palm on each of their heads and it was over. As soon as their souls left their bodies, they slumped over, indicating that it was over. Puling himself out of his _'killer'_ mode as he had come to call it, he immediately fell onto his knees and started to cry. He was an emotional wreck. The full weight of what he had done again still weighs heavily on him. He knew that they were safe within that special place that he sent the souls that he collects, but that does not change the fact that in the span of an hour he'd just killed his family.

He would give them a burial however, even though he would revive them or end up having to RESET. It was something he had to do, or else his sanity might just slip.

 _Flashback End_

He gasped as he felt three pairs of arms encircle him. Looking behind him he saw the trio from the portrait, all of them giving him worried looks.

"I'm sorry if I had worried you all, just having an unpleasant memory."

"Tristan, I know that we don't know each other all that well, but if you want to talk about it don't hesitate." Toriel replied with an encouraging tone.

"It's not good to keep bad feelings bottled up, but this is something I'm not comfortable talking about just yet. Now if I may ask who are these two little ones?"

Giving him a gentle smile, Toriel introduced his two little sisters.

"Well this is Frisk and Chara respectively. Girls say hello to Tristan, he will be staying here for the foreseeable future."

"Hi Tristan, I hope we can be great friends" Frisk said.

"Hi" Chara stated bluntly.

Soon they were seated in the lounge area, just getting to know one another. Well he more pretended to not know anything. He had gone through this scene plenty of times before. The only difference this time was his slight mental break down in front of the portrait. There was something that was bothering him greatly though. How could he forget about his little sisters? It never happened before, so why now? On top of that the two of them kept sending him strange glances when they thought he was not paying attention to them. No, something is definitely wrong. Now that he thought about it, Toriel had not asked about Flowey. She always does, she worries whether the flower had hurt him or not. She also asks him what happened to the flower, so something was amiss here. He kept the confusion off his face and continued the conversation. Eventually a lovely scent had entered the room, it smelt of baked dough, cinnamon and butterscotch. Taking a deep whiff of the aroma, he asked Toriel if she had something in the oven.

"O dear! The pie is burning! Please excuse me for a bit I will be back soon."

"No problem at all"

While Toriel was tending to the pie, Tristan started to look about the familiar room. Excluding the portrait, there was a modest dining table that could seat four people and bookshelf that was filled with books. There are three brown sofas, one that seats one person with a stool in front of it with a small table that had a lamp on it, the one that Frisk and Chara was sitting on that could seat two people, and the one that he himself was sitting on that also only seated two. The walls were a shade of light brown, almost a cream tone, and finally the flooring was light colored wooden planks. Definitely a place made for peace and quiet.

Once again he caught his two little sisters giving him a strange look. Deciding to address the elephant in the room, he gave them a questioning look and asked if something was wrong.

"No, no problem at all Tristan."

That statement was a bit rushed and he could tell that they were nervous about something. He decided not to pry. After all he did not want to talk about his dilemma when they asked. Soon Toriel had come back, stating that the pie just needed to cool down a bit. Continuing with the previous conversation before Toriel had to tend to the pie, he noticed that even she was a bit nervous.

Well know he definitely knew that something was different. He made a mental note to be aware. He was not being paranoid, there was times when things had not gone according to previous RESETs. Never before has anything been so _'diverging from the main flow'_ so to speak. Also this was the first time that he could not remember things that are very important. He had to be aware.

After a few minutes the pie was ready to eat. Everyone was seated on the dining table with a slice of pie in front of them. Thanking Toriel for the meal Tristan started to eat, savoring his meal. He could not help the smile as the cinnamon butterscotch pie was delicious, and it brought some good memories of the past. Times when he, Toriel and his two little sisters where having fun, reading snail facts from one of the many books and catching butterflies of all things. As he took another bite, he was ripped out of his musings by something that was not right. Once again the rest of the occupants where giving him a strange look. They were nervous about something and that was when he found something that is not supposed to be in the pie between his teeth. Discreetly slipping the object between his teeth and cheek he continued to eat. Making sure to pretend that he didn't noticed at all.

' _What is that? It feels like a pill of sorts, definitely tastes like one.'_

Now he was very suspicious, that was never there before. After the meal he stated to help Toriel clean, noticing that she kept an eyeing the time. After they were done, Toriel asked him if he was a bit sleepy.

' _Maybe she thinks that I am a bit tired after today's events.'_

He shot that thought down when he saw her giving him one of those looks again. He decided to play along for now, and agreed that he a bit tired. Toriel quickly walked off after telling him to stay there. That never happens. He noticed that his sisters are not there either. That also does not happen. Normally Toriel would offer that he stay in the girls room while they stay the night with her. Only until they get a bed for him in the extra room, which then becomes his room. Toriel eventually came back holding a blanket and pillow.

"I'm very sorry, but we do not have a spare bed. Would you mind to spend the night on the sofa? Its only until we get another bed for you."

"I don't mind at all. I kinda figured as much. Quick question, why would you get another bed for me? Not that I am complaining of course."

"I am certain that you do not have a place to go to, seeing that you are new to the underground. So for the foreseeable future I thought you could stay here."

"Thank you a lot. I really appreciate it."

"Well sleep well Tristan, and don't let the bedbugs bite."

Chuckling a bit Tristan replied "Same to you."

He watched her walk away, most likely heading to her room. He still had the pill in his mouth though. Deciding it would be best to spit it out, he made his way into the kitchen. Grabbing a glass from the cupboard, he could not help but wonder what the pill was for. After filling a glass and adding some water, he took a sip to help him spit the pill out.

' _Definitely not a pleasant taste, wonder what the pill does?'_

Peering into the sink, he saw a small pinkish tablet. He recognized it as one of the sleeping pills that Toriel takes when she cannot sleep at night. Feeling his suspicion growing even more, Tristan decided to sneak his way towards the bedrooms. Nearing the rooms, he started to hear the voices of the trio. All of them were coming from one of the bedrooms, Toriel's room to be precise. He silently approached door and started to eavesdrop on the conversation. He started to feel dread at what he was about to hear. Not a good sign, considering the last time this feeling arose. Placing his head against the door to better make out the muffled sound, he started to listen to the conversation.

"Are you sure that the sleeping tablet will work mom?" came Frisk's soft voice.

"I am certain my child. I only use those ones in particular when I have a severe head ache."

"How long do you think it will take? I want to get this over and done with." Chara stated.

"Well it should put him in a deep slumber in about half an hour. I do hope this works my children, he has done this far too much already. I just hope that he has not hurt a lot of monsters yet. The little flower was nowhere to be seen when I found him."

They settled into a silence, but Tristan could not believe his ears. He knew that both Frisk and Chara could remember the RESETs, but he found a way to prevent that. Toriel was a different story all together. In all of his RESETs she had not once remembered what had happened. How was it that these three knew? Why now of all times? This did not make any sense to him. Could this also prove to be a major problem in the near future? He hoped not, because if it did it most likely alerted a certain pun loving skeleton to the RESETs as well. Sans also has the ability to remember the RESETs, but just like his two little sisters, he found a way around that. He needed to clear his head, but as he was about to stand up the he heard a voice.

"But mom… Is it really ok to hurt him? I mean he is a bad man, but doesn't killing him also make us bad people?"

Frisk's question stopped him dead in his tracks. Now that was not a thought that he liked at all. He would have to move up his plans. He felt a tear rolling down his cheek, he wanted to spend a little more time with them before having to end it again.

"I am sorry Frisk, but it must be done." Came Toriel's somber reply.

"Frisk after this we can give him a burial, if that help a bit. But sometimes to do something right means that you have to do something bad." Chara added.

On his side of the door, Tristan was barely holding back his sobs. Tears were freely rolling down his face, the only thing preventing him from making a sound was his hands that was holding his mouth shut. While his shoulders were still shaking from the sobbing, he silently made his way to the couch. Lying down in his supposed death trap, he struggled to calm himself before the inevitable meeting.

Soon he heard the door softly open, they were trying not to startle him. He heard them making their way towards him, slowly they inched closer. He heard the rustle of fabric right next to him. His danger sense was going haywire within his mind, he knew that he would act soon. Hearing a grunt from Toriel, he heard the whistling of a blade on a direct path to his heart. In the blink of an eye his hand shot out from under the blanket, grabbing his attacker's wrist in a firm grip. Before anyone could react, he leapt out of the bed and swiftly knocked the trio down. When they looked up and him, they all gasped. They were not expecting him to have reacted like that. He should have been in a deep sleep already.

"How? How do you remember the RESET?"

"Is that what you call it? Do you kill just because you have this ability to RESET? Do you…"

"Enough! Please, you do not understand what is going on Toriel. That statement alone is proof already."

"Then why do you kill at all? Killing is bad. Why do you like to kill so much?" Frisk asked in anger.

Now that was a painful stab at his heart. Frisk had always been able to calm him down when he was angry, cheer him up when he was sad and gave off a friendly atmosphere. Hearing her ask him that, it was not right at all.

"I have my reasons Frisk. I do not like to kill either. It makes me feel like a horrible person. I guess you could call me one. It does not change the facts."

"Maybe if you told us, we could help you."

"Frisk, please understand that no matter what you do will not change the outcome. I must kill Toriel, and I can't just let you two stay here all alone. There is no other way." He stated.

Tears started to roll down his face again. No matter how many times he did this, he could not get used to it. The feelings that came with the revelation of him killed his family. He started to steel his heart and block the outside world. Frisk and Chara started to back away in fear, with Toriel trying to shield them. It seems that the memory that he had relived earlier that knight was the same one they had a memory of.

"Mom! That is how he gets when he is about to kill us! Please do something." Chara yelled out in panic.

"I will try my child, but please take your sister and run! Run as fast as you can and don't look back!"

Before they could even react, Tristan had placed a glowing hand on Toriel's head. She slumped down and turned to dust, leaving a crying Frisk and Chara behind. Chara had tried to get her sister to move, but Frisk would not budge. She was frozen in fear.

"I'm sorry you two, but this is for the best." Tristan said stretching his glowing hands towards the two.

As his hand connected with their heads, Frisk muttered "Is this all.. that we… mean to.. you, big brother?" All the while Chara gave him a look of a pure pained betrayal.

With that said the two had died within his grasp. As their bodies hit the ground, Tristan was in a pained shock. Why would she still call him that? He fell to his knees, staring at his handiwork. Soon a fresh batch of tears welled up in his eyes. He started to cry once again, but this time he felt even more pain within his chest than any other time in his life.

 **A/N:** **I'm sorry that this chapter took so long. I was a bit distracted, not a proper excuse I know. Anyways, if you have any puns for Sans to use in future chapters. Don't be afraid to PM me. It might just make it into the story.**

 **O yeah forgot to mention. Cliffhangers O'Plenty.**

 **Assassin0401417 out**


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